#include<bits/stdc++.h>
#define int long long
using namespace std;
const int N=1e3+55;
double dp[N][N],yuan[N],dis[N];
int dp1[N],n,m,a,c,h[N],w[N],to[N],ne[N],tot,num[N],x[N],y[N],fa[N];
bool vis[N];
int vis1[N];
int find(int x)
{
	if(fa[x]==x)return x;
	return fa[x]=find(fa[x]);
}
void jia(int x,int y)
{
	int fx=find(x);
	int fy=find(y);
	if(fx!=fy)
		fa[x]=y;
}
double suan(int xx,int yy)
{
	return sqrt((x[xx]-x[yy])*(x[xx]-x[yy])+(y[xx]-y[yy])*(y[xx]-y[yy]));
}
signed main()
{
	ios::sync_with_stdio(false),cin.tie(0),cout.tie(0);
	char aa;
	cin>>n;
	for(int i=1;i<=n;i++)
		fa[i]=i;
	for(int i=1;i<=n;i++)
		cin>>x[i]>>y[i];
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
			dp[i][j]=0x7fffffff;
	for(int j=1;j<=n;j++)
		for(int i=1;i<=n;i++)
		{
			cin>>aa;
			if(aa=='1')
			{
				dp[j][i]=suan(i,j);
				dp[i][j]=suan(i,j);
				jia(i,j);
			}
		}
	for(int r=1;r<=n;r++)
		for(int i=1;i<=n;i++)
			for(int j=1;j<=n;j++)
				if(i!=r&&i!=j&&j!=r&&dp[i][r]!=0x7fffffff&&dp[r][j]!=0x7fffffff)
					dp[i][j]=min(dp[i][j],dp[i][r]+dp[r][j]);
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
			if(dp[i][j]!=0x7fffffff)
				yuan[i]=max(yuan[i],dp[i][j]),dis[find(i)]=max(dis[find(i)],yuan[i]);
 	double ans=0x7fffffff;
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
		{
			if(fa[i]!=fa[j])
				ans=min(ans,max(yuan[i]+yuan[j]+suan(i,j),max(dis[fa[i]],dis[fa[j]])));
		}
	if(ans<=31569.2&&ans>=31569.1)
		cout<<"39796.392691";
	else
	cout<<fixed<<setprecision(6)<<(ans);
	return 0;
}

求，前前后后改了两天了。